The present invention relates in general to the field of speech pathology, and is directed to determining whether a patient is at risk for one or more abnormal physiological conditions, including but not limited to oral or pharyngeal dysphagia, and pneumonia. In particular, the present invention is directed to an enhancement to the invention disclosed in the above-referenced ""404 application, that provides focusing or xe2x80x98targetingxe2x80x99 delivery of the chemostimulant to stimulate nociceptor (irritant) and c-fibre receptors in the patient""s throat, through a relatively narrow diameter tube that may be coupled with the observation tube of a laryngoscope. Coupling this nebulizer tube with that of the observation tube of a laryngoscope facilitates direct visualization of the mucosa of the laryngeal vestibule through a laryngoscope during inhalation and/or the laryngeal cough reflex, to determine whether the patient""s larynx is functioning normally or abnormally.
As described in the above-referenced ""404 application, the conventional technique employed by speech pathologists for clinically identifying patients at risk for aspiration has involved the evaluation of a patient""s swallow. A normal human swallow can be separated into four phases: 1)xe2x80x94oral preparation, 2)xe2x80x94the oral phase, 3)xe2x80x94the pharyngeal phase, and 4)xe2x80x94the esophageal phase. Patients who have suffered a stroke, traumatic brain injury or neuromuscular disorder (such as MS or ALS) have an increased risk of aspiration, and may have difficulty with either the oral phase, the pharyngeal phase or both, secondary to neurologic deficits.
Poor tongue movement in chewing or in the swallow can cause food to fall into the pharynx and into the open airway before the completion of the oral phase. A delay in triggering the pharyngeal swallowing reflex can result in food falling into the airway during the delay when the airway is open. Reduced peristalsis in the pharynx, whether unilateral or bilateral, will cause residue in the pharynx after the swallow that can fall or be inhaled into the airway. Laryngeal or cricopharyngeal dysfunction can lead to aspiration because of decreased airway protection during the swallow.
An abnormal human swallow is termed dysphagia. The oropharyngeal physiology involved in a normal swallow is very complicated, and many different neurological disturbances can disrupt normal swallowing and can cause aspiration of food material, liquid or solid, into the lungs, leading to increased morbidity in hospitalized patients and possible pneumonia. See, for example, the article by Jeri Logemann, entitled: xe2x80x9cSwallowing Physiology and Pathophysiology,xe2x80x9d Otolaryngologic Clinics of North America, Vol. 21, No. 4, November 1988, and the article by L. Kaha et. al., entitled: xe2x80x9cMedical Complications During Stroke Rehabilitation, Stroke Vol. 26, No. 6, June 1995.
Speech pathologists have tried many procedures to detect or predict aspiration in patients with neurological deficits. Although the standard bedside swallow exam to screen patients is beneficial for evaluating patients at risk for oral or pharyngeal dysphagia, studies have shown that, when compared to a modified barium swallow (MBS) videofluoroscopic examination, it is neither very specific nor sensitive in detecting aspiration. (The MBS test customarily involves having the patient ingest a volume of barium in a semi-solid or liquid form. Through fluoroscopy, the travel path of the swallowed barium may be observed by a medical practitioner to determine whether any quantity has been aspiratedxe2x80x94which could lead to acute respiratory syndrome or pneumonia.) See, for example, the article by Mark Splaingard et. al. entitled: xe2x80x9cAspiration in Rehabilitation Patients: ideofluoroscopy vs. Bedside Clinical Assessment; Archives of Physical Medicine and Rehabilitation, Vol. 69, August, 1988, and the article by P. Linden, et. al., entitledxe2x80x9d xe2x80x9cThe Probability of Correctly Predicting Subglottic Penetration from Clinical Observationsxe2x80x9d, Dysphagia, 8: pp 170-179, 1993.
As discussed in the above-referenced Logemann article, and also in an article entitled: xe2x80x9cAspiration of High-Density Barium Contrast Medium Causing Acute Pulmonary Inflammationxe2x80x94Report of Two Fatal Cases in Elderly Women with Disordered Swallowing,xe2x80x9d by C, Gray et al, Clinical Radiology, Vol. 40, 397-400, 1989, videofluoroscopic evaluations are more costly than bedside evaluations and videofluoroscopy is not entirely without risk. Because of the poor predictability of bedside exams, the MBS is being used more and more with its increased reliability for diagnosing aspiration. Many studies using videofluoroscopy have tried to pinpoint the exact anatomical or neurological deficit causing the dysphagia, as well as what stage of the swallow is primarily affected in different disorders.
Patients with a head injury, stroke or other neuromuscular disorder can aspirate before, during, or after the swallow, and a high percentage can be silent aspirators. Unfortunately, these patients might not display any indication of aspiration during a clinical exam, but can be detected by the MBS, as discussed in the Logemann article and in an article by C. Lazurus et al, entitled: xe2x80x9cSwallowing Disorder in Closed Head Trauma Patients,xe2x80x9d Archives of Physical Medicine and Rehabilitation, Vol. 68, February, 1987, an article by J. Logemann, entitled: xe2x80x9cEffects of Aging on the Swallowing Mechanism,xe2x80x9d Otolaryngologic Clinics of North America, Vol. 23, No. 6, December 1990, and an article by M. DeVito et. al., entitled: xe2x80x9cSwallowing Disorders in Patients with Prolonged Orotracheal Intubation or Tracheostomy Tubes,xe2x80x9d Critical Care Medicine, Vol. 18, No. 12, 1990.
The bedside swallow exam that has been customarily performed by most speech pathologists evaluates history, respiratory status, level of responsiveness and an oral exam. The oral examination includes a detailed evaluation of the muscles of mastication, lips, tongue, palate, position in which the patient is tested, as well as swallowing evaluation. Sensation, various movements and strength are carefully evaluated. In the pharyngeal stage, the patient is tested for a dry swallow, thin liquid, thick liquid, pureed textures and solid textures.
A typical bedside exam looks for nasal regurgitation, discomfort or obstruction in the throat or multiple swallows, as well as any visible signs that may indicate risk for aspiration, gurgling, impaired vocal quality, and coughing. The bedside exam results are then analyzed to determine whether the patient should have an MBS study to evaluate swallowing physiology and to rule out aspiration. Although the bedside exam is very thorough, and can identify patients who are at risk for or have dysphagia, it is not effective in determining which patients will aspirate.
In addition to the foregoing, speech pathologists have historically had difficulty studying the sensory afferents of the larynx involved in airway protection. As described in an article by J. Widdicombe et al, entitled: xe2x80x9cUpper Airway Reflex Control,xe2x80x9d Annual New York Academy of Science, Vol. 533, 252-261, 1988, the sensory afferents for general coughing travel the internal branch of the superior laryngeal nerve. A patient may have a voluntary cough present with the efferent motor system intact, but not have any sensation on the larynx secondary to the afferents becoming completely or partially affected, which would be indicative of risk for silent aspiration.
Although an MBS test is of value to patients that silently aspirate, it is difficult to decide which patients should have an MBS test. Not all patients with a closed head injury or a stroke will aspirate. Moreover, it is not economically realistic to employ an MBS test to evaluate all patients with neurologic deficits for aspiration. Advantageously, the chemostimulant-based, cough-invoking screening process described in the ""404 application and its parent predecessors, referenced above, successfully overcomes shortcomings of such conventional processes that have attempted to detect aspiration in patients with neurological deficits.
Referring to FIG. 1, pursuant to the invention disclosed in these applications, a patient 10 (wearing a nose clip 12) is subjected to an chemostimulant-based, inhalation cough test. In this test, a prescribed quantity of a chemostimulant that stimulates nociceptor (irritant) and C-fibre receptors of the patient""s larynx is injected into the patient""s mouth. Inhalation of the chemostimulant may be readily accomplished by using a standard nebulizer 14, that has been loaded with an aerosol chemostimulant, such as an atomized solution of tartrate mixed with saline. Not only has this solution has been demonstrated to stimulate a cough 100% of the time in normal individuals, but tartrate is considered safe, does not cause pain or discomfort, and has not been shown to cause bronchoconstriction or complications in asthmatics when inhaled in an aerosol form.
The quantity of chemostimulant is injected into the patient""s mouth for a prescribed period of time (e.g., on the order of 15 seconds). The nebulizer output spray rate may be on the order of 0.2 ml/min. as a non-limiting example. The patient may be tested a prescribed number of times (e.g., up to three times) at different stimulant strengths until a cough is elicited. During each successive chemostimulant application, the patient receives progressively increasing concentrations of the aerosol for the prescribed period of time by tidal breathing at one minute intervals using successively increasing percentage concentrations (e.g. 20, 50 and 80 percent).
Once a cough is elicited from the patient as a result of the inhaled aerosol stimulant, the patient""s response to the inhalation test is graded. The patient may be graded as being at low risk for pneumonia (where the patient coughs immediately in response to the initial aerosol spray) or at a high risk for pneumonia (where a cough is present but decreased, or the patient does not readily cough in response to the initial concentration spray, but requires a more concentrated aerosol application).
Now although the chemostimulant-based, cough-invoking screening process described in the ""404 application is effective to determine whether a patient is at risk for one or more abnormal physiological conditions, including but not limited to oral or pharyngeal dysphagia, and pneumonia, it may be desirable to provide the practitioner with the ability to focus delivery of the chemostimulant to a particular region of the throat and directly observe that region of the patient""s airway during the course of delivery of the chemostimulant. This would not only provide the practitioner with a visualization of whether a particular region of the patient""s throat (in particular, the laryngeal vestibule) is functioning properly, but it would allow the practitioner to be satisfied that the chemostimulant is accurately delivered to the intended region of interest.
In accordance with the present invention, this objective is successfully accomplished by coupling the delivery port of the chemostimulant nebulizer with a throat insertable conduit. This conduit provides for focused delivery of the chemostimulant to that region of the patient""s throat (the mucosa of the laryngeal vestibule) to be visualized by a monitoring device such as a laryngoscope. The chemostimulant conduit may comprise a relatively narrow flexible tube of the type used for airway-invasive procedures, so that the delivery port of the chemostimulant delivery tube may be inserted adjacent to the targeted and observed region of the throat.
To this end, the chemostimulant-delivery tube may be physically coupled with the laryngoscope observation tube, so that both tubes may be simultaneously inserted into the patient""s airway; alternatively, it may be fed separately of the laryngoscope tubing to the observation region. In either case, the invention provides for focused delivery of chemostimulant and direct visualization of the laryngeal vestibule through the laryngoscope during inhalation and/or the laryngeal cough reflex, to enable the practitioner to determine whether the patient""s larynx is functioning normally or abnormally.